This invention relates to automotive engine controllers for controlling the fuel injection, the ignition timings, the idling speed, etc., of an automotive engine, and more particularly to the common type engine controllers which can be used both with vehicles with an automatic transmission and those with a manual transmission and which are capable of identifying the type of the transmission to adapt the control parameters of the engine in accordance the type of the transmission.
Generally, the various controlled parameters of an automotive engine, such as the timings of the fuel injection, the ignition timings and the idling RPM of the engine, are controlled by means of an electronic control unit in accordance with the operating condition of the engine. The electronic control unit of the engine controller consists of a microcomputer, and in the case of a common type engine controller, the same electronic control unit is used both in the vehicle with the automatic and that with the manual transmission. The engine controller receives various sensor signals indicating the operating condition of the engine and adapts the control parameters thereto. In particular, a detector means for detecting the neutral position of the transmission may be provided such that the control parameters may be adjusted in accordance with the position of the transmission.
Thus, when used with an automatic transmission, the engine controller adjusts the controlled parameters such as the target idling RPM of the engine in accordance with the position the transmission, (i.e., the engine controller changes the controlled parameters according as whether the transmission is in the neutral or the parking range, on the one hand, or in the driving range, on the other).
When used with a vehicle provided with a manual transmission, on the other hand, the inputs of the engine controller are wired in such a manner that the neutral signal which indicates the neutral state of transmission is constantly input to the engine controller. Thus the engine controller controls the idling speed of the engine, etc., with the manual transmission just as when the engine controller is used with an automatic transmission and the automatic transmission is in the neutral range.
The idling RPM of the engine, however, may be set lower for the manual transmission than for the automatic transmission. Thus, to reduce the fuel consumption, the recent trends have been to set the idling RPM for the manual transmission at about 600 RPM, which is substantially lower than that for the automatic transmission, which is, for example, about 650 RPM. The idling RPM for the automatic transmission cannot be set lower than 650 RPM, for example, since the oil pressure must be kept above a predetermined level such that the delay in the oil pressure response immediately after the transmission shift from the neutral to the driving range is minimized. Thus, to meet the more severe demands of recent years for the reduction of the fuel consumption, the electronic control unit must be designed separately for the automatic and the manual transmission. Thus, the kinds of the engine controllers, and hence the production cost thereof increase.
Japanese Patent Publication (Kokoku) No. 4-42535 thus proposes a common type engine controller which can be used both with the automatic and the manual transmission and distinguishes the type of the transmission by means of software. According to this Japanese Patent Publication, a neutral switch is provided for detecting the state of the transmission of the vehicle. When used with an automatic transmission, the neutral switch is turned on only when the transmission is at the neutral position. When used with a manual transmission, on the other hand, the circuit is wired in such a manner that the neutral switch is permanently turned on. If it is detected that the neutral switch is turned on during acceleration, it is judged that the transmission is manual. If the neutral switch is turned off during acceleration, it is judged that the transmission is automatic. The type of the transmission can thus be determined automatically.
In the case of the engine controller of the above Japanese Patent Publication, however, the determination of the type of the transmission is possible only after the vehicle is in acceleration. Only then the proper adjustment of the control parameters to the type of the transmission becomes possible, and hence it is not possible to adjust the idling speed of the engine, for example, to the type of the transmission.